A plentitude of battery powered, hand-held solid state devices are provided with display screens adapted for specialized applications. Examples of such devices include, computers, distance measuring devices, navigational instruments, paging devices, and communications devices generally, including telephone handsets adapted to receive e-mail. This list is not exhaustive, but serves to illustrate the utilitarian nature of alphanumeric, and graphics display screens which are essential where an alphanumeric data or graphics readout is required.
Under conditions of sufficient ambient light level, these screens perform adequately. At low level light conditions, however, illumination is required to read the data carried by the screen. Where an external power source provides operating current for the device, screen illumination is not generally a problem. However where the device relies on a self-contained source of battery power, illumination becomes problematic since the current requirements of illumination components generally impose a substantial current drain from the battery. Light emitting diodes (LEDs) are particularly notorious in this regard. Power conservation in battery powered devices of the type described is therefore a major concern for equipment designers and users alike.